In recent years, smaller and lighter mobile data terminals such as mobile phones, notebook personal computers, and smartphones have been increasingly used and batteries used as driving power supplies therefor have been required to nave higher capacity. Nonaqueous electrolyte secondary batteries, which are charged and discharged in such a manner that lithium ions move between positive and negative electrodes in association with charge and discharge, have high energy density and high capacity and therefore are widely used as driving power supplies for the above mobile data terminals.
Furthermore, the nonaqueous electrolyte secondary batteries are recently attracting attention as driving power supplies for electric vehicles, electric tools, and the like and applications thereof are expected to be further expanded. Such on-vehicle/driving power supplies are required to have high capacity so as to be used for a long time and high power characteristics. Furthermore, particularly in on-vehicle applications, quick charge is increasingly demanded and both high capacity and high regeneration are required to be achieved.
Herein, as a method for increasing the capacity and power of a battery, for example, Patent Literature 1 proposes a positive electrode active material for nonaqueous electrolyte secondary batteries. In the positive electrode active material, the Li site occupancy of a Li site in a crystal is regulated to 98.5% or more and the metal site occupancy of a metal site is regulated to 95% to 98%.
On the other hand, Patent Literature 2 suggests that discharge capacity and thermal stability are increased using a positive electrode active material represented by the formula Li1.1+xNiaM1bM2cO2 (where M1 includes at least either of Mo and W, M2 is Mn, −0.07≤x≤0.1, 0.90≤a≤0.98, 0.02≤b≤0.06, and 0.00≤c≤0.06).